function [ status ] = mx_eyelink_user_menu_selection( )
%MX_EYELINK_USER_MENU_SELECTION Checks for a user-menu selection, clears response
% for next call.
%
% Returns:
% 0 if no selection made since last call, else code of selection.
%----------------------------------------------------------------------------
% Copyright Eduardo Aponte 2013
% aponteeduardo@gmail.com